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Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |
Total revenues | $ 6,267,411 | $ 5,906,956 | $ 5,475,846
Personnel expenses | 1,517,910 | 1,436,603 | 1,277,382
Product and content delivery expenses | 410,223 | 380,887 | 348,175
Other expenses | 61,734 | 54,083 | 35,155
Gross contribution | 4,277,544 | 4,035,383 | 3,815,134
Cost of services and product development - unallocated | 33,155 | 31,667 | 33,059
Selling, general and administrative | 2,884,814 | 2,701,542 | 2,480,944
Depreciation and amortization | 202,315 | 191,103 | 191,946
Acquisition and integration charges | 973 | 9,587 | 9,079
Gain from sale of divested operation | 0 | (135,410) | 0
Interest expenses and other, net | 68,913 | 92,842 | 72,911
Gain on event cancellation insurance claims | (300,000) | (3,077) | 0
Income before income taxes | $ 1,387,374 | 1,147,129 | 1,027,195
Maximum |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |
Percent of target bonus charges allocated to segments | 100.00% |  |
Research |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |
Total revenues | $ 5,125,650 | 4,887,046 | 4,604,791
Conferences |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |
Total revenues | 583,224 | 505,164 | 389,273
Consulting |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |
Total revenues | 558,537 | 514,746 | 481,782
Operating Segments | Research |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |
Total revenues | 5,125,650 | 4,887,046 | 4,604,791
Personnel expenses | 1,125,694 | 1,071,315 | 963,437
Product and content delivery expenses | 179,784 | 193,234 | 212,143
Other expenses | 27,329 | 22,354 | 14,637
Gross contribution | 3,792,843 | 3,600,143 | 3,414,574
Operating Segments | Conferences |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |
Total revenues | 583,224 | 505,164 | 389,273
Personnel expenses | 67,326 | 56,708 | 43,176
Product and content delivery expenses | 215,664 | 178,675 | 125,528
Other expenses | 18,825 | 16,042 | 9,843
Gross contribution | 281,409 | 253,739 | 210,726
Operating Segments | Consulting |  |  |
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] |  |  |
Total revenues | 558,537 | 514,746 | 481,782
Personnel expenses | 324,890 | 308,580 | 270,769
Product and content delivery expenses | 14,775 | 8,978 | 10,504
Other expenses | 15,580 | 15,687 | 10,675
Gross contribution | $ 203,292 | $ 181,501 | $ 189,834

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Data Type: | na
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